Page:AmJourSci 4 39 233 551-554.djvu/1

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E. W. Shuler—New Ordovician Eurypterid.

Art. XXXVI.—A New Ordovician Eurypterid; by Ellis W. Shuler.

During the summer of 1914, the writer collected fossils from the Bays sandstone at various points along Walker Mountain in southwestern Virginia. The collection at Lyons Gap yielded a few Eurypterid fragments. This is one of the best known localities for collecting in the Bays sandstone. Prof. J. J. Stevenson visited the locality in 1884 and secured a number of fossils among which were "Ambonychia radiata" and "Rhynconella capax" (= Orthorhynchula linneyi), and since that time it has been visited by a number of other geologists. These facts are mentioned because the Bays sandstone formation is for the most part unfossiliferous in Walker Mountain. The fossiliferous localities are limited to the southwestern section of the mountain along a band about twenty miles in length.

At Lyons Gap the fossil-bearing bed is about ten feet in thickness and occupies approximately the middle of the Bays formation, ninety feet below the Clinch sandstone. The point, however, of separation of the Bays sandstone from the Sevier shales below is a somewhat arbitrary one. The bed is an argillaceous sandstone which has a pronounced brick red color. It seems worthy of note that the bed carrying marine fossils is distinctly redder than the non-fossiliferous part of the sandstone. The southwestern section of the Bays sandstone along Walker Mountain, carrying the fossiliferous horizon, is also, on the whole, a deeper red than the section along the mountain to the northeast, which is practically barren of fossils.

Stylonurus (Ctenopterus)? alveolatus sp. n.

The Eurypterid fragments consist of parts of four post-oral limbs; a part of the telson spine with the impression of two abdominal segments, and a fragmentary carapace.

The best preserved fragment is that belonging to the second or third endognathite, fig. 4. It consists of three segments, all of which, after making allowance for mashing due to the conditions of preservation, show a distinct dorsi-ventral flattening. The articulation of the joints is such as to permit flexing movements downward and backward, an arrangement which suggests an adaptation of the limb to swimming. The individual segments are distinctly elongated, being on the average twice as long as wide. The lengths of the successive segments beginning with the proximal one are: 16mm, 16mm, and 20mm. The corresponding widths are: 10mm, 8mm, and 6mm.

Am. Jour. Sci.—Fourth Series, Vol. XXXIX, No. 233.—May, 1915.